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21.
The dynamical behaviour of nonlinear electrical circuits is usually modelled in the time domain by differential-algebraic equations (DAEs). The differential-algebraic formalism drives qualitative analyses based on linearization to a matrix pencil setting. In this context, the present paper performs a spectral analysis of matrix pencils and DAEs arising in nonlinear circuit theory. Specifically, the non-singularity, hyperbolicity and asymptotic stability of equilibria are addressed in terms of circuit topology. The differential-algebraic framework puts the results beyond those already known for state-space models, unfeasible in many actual problems. The topological conditions arising in this qualitative study are proved independent of those supporting the index, and therefore they apply to both index-1 and index-2 configurations. The approach illustrates how graph theory, matrix analysis and DAE theory interact in the dynamical study of nonlinear circuits. 相似文献
22.
X-ray photoelectron spectroscopy (XPS) applied to the study of fluorinated polymer surfaces presents several problems related both to peak assignment and to degradation. In this work, we analyse extensively the question of XPS peak assignments in this kind of surfaces. We conclude that in this kind of surfaces using binding energy differences between fluorine and carbon is better than using absolute binding energies. Also a useful relation between fluorine photoelectron energy vs. polymer composition expressed through the atomic ratio fluorine/carbon (F/C) was found. A protocol for data treatment is proposed and applied to a XPS study of the degradation induced by X-ray on high-density polyethylene surfaces modified by direct fluorination. Results obtained for the degradation, namely the atomic ratio F/C obtained by two different methods, combined with angle resolved X-ray photoelectron spectroscopy (ARXPS) were used to study the fluorine concentration profile in depth, producing self-consistent results. 相似文献
23.
Jefferson Fabrício Cardoso Lins Hugo Ricardo Z. Sandim Hans-Jürgen Kestenbach 《Journal of Materials Science》2007,42(16):6572-6577
The present paper reports the experimental results on the microstructural and textural characterization of a hot-rolled IF
steel. The IF steel was hot-rolled in multiple passes in the austenitic field (1,070 °C) followed by air-cooling. SEM, TEM,
and LOM were used to image the microstructure of the material. The global texture was determined by X-ray diffraction (XRD)
technique. The mesotexture of selected regions was investigated by electron backscatter diffraction (EBSD). Results show the
presence of a diffuse (nearly random) and weak texture in the hot-band that consists of recrystallized polygonal grains and
subgrains. The fraction of boundaries with misorientations comprised in the interval 2° ≤ ψ < 15° was found to be lower than
5%. It can be concluded that these low angle boundaries and the presence of subgrains can be associated to the existence of
a few areas softened by recovery during or after hot rolling in austenitic field. 相似文献
24.
OM Takayanagui AA Castro e Silva RC Santiago NS Odashima VC Terra AM Takayanagui 《Canadian Metallurgical Quarterly》1996,54(4):557-564
Cysticercosis is a severe public health problem in several regions of Asia, Africa and Latin America. Epidemiologic studies based on the frequency of cases observed in specialized neurology, neurosurgery and computed tomography services, at autopsy and in seroepidemiologic studies do not permit the determination of the true prevalence of the disease in the population. The objective of the present study was to investigate the prevalence of cysticercosis by compulsory notification. The coefficient of prevalence was 54 cases/100,000 inhabitants in the municipality of Ribeir?o Preto. The results also indicated that cysticercosis is not under control in our region since 21% of cases presented the active form of the disease. Compulsory notification proved to be a valuable resource for the epidemiologic study of cysticercosis, also permitting the mapping of more affected areas for a better direction of prevention strategies. 相似文献
25.
Examined the impact of increasing the percentage of hires (above the T. A. Cleary [1968] fair-hiring level) from minority groups with demonstrated lower average job performance. Increased minority hiring resulted in only a small performance loss, even when minority hiring exceeded the minority applicant representation. However, when minorities were hired at a rate equal to or greater than their applicant representation, the expected performance loss among the hired minorities was much greater than performance loss across all hires. More important, the discrepancy in performance between majority and minority hires increased as minority hiring increased. With minority hiring above the level of minority applicant representation, this discrepancy exceeded the population difference in performance between the 2 groups. These findings suggest additional considerations when raising minority hiring above minority applicant representation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
26.
Glutathione content and glutathione-dependent enzymes were measured in the liver of two fish species, gudgeon (Gobio gobio) and roach (Rutilus arcasii), from the river Bernesga (Spain) caught downstream and upstream of the waste site of several chemical industries. Animals from contaminated sites display a reduced glutathione concentration and a tendency to the decrease of glutathione S-transferase activity. Glutathione peroxidase activity was significantly elevated only in the liver of Gobio gobio and glutathione reductase activity in that of Rutilus arcasii. Our data indicate that the glutathione system constitutes a sensitive biochemical indicator of chemical pollution. Relative changes of glutathione and glutathione-dependent enzymes in both fish species suggest a different susceptibility to toxins. 相似文献
27.
BM Sandmaier R Storb KL Bennett FR Appelbaum EB Santos 《Canadian Metallurgical Quarterly》1998,91(9):3494-3502
Primary graft rejection after marrow transplantation occurs more frequently in patients receiving HLA-haploidentical compared with HLA-identical sibling transplants. Both human and experimental animal data suggest that the cells responsible for this phenomenon are either host natural killer (NK) cells, T cells, or both. To investigate the mechanisms of graft rejection, we have developed a canine model of marrow transplantation, which uses DLA-nonidentical unrelated donors in the absence of postgrafting immunosuppression. In this model most animals rejected their marrow grafts after a preparative regimen of 9.2 Gy total body irradiation (TBI). However, engraftment of DLA-nonidentical marrow can be facilitated when the recipients are pretreated with monoclonal antibody (MoAb) S5, which recognizes CD44. In this report, we extended these observations by first cloning the canine CD44 and, next, mapping the epitope recognized by S5, which was located in a region conserved among human and canine CD44 and was distinct from the hyaluronan binding domain. However, in vitro binding of S5 caused a conformational change in CD44, which allowed increased hyaluronan binding. Then, we reexamined the in vivo model of marrow transplantation and compared results with MoAb S5 to those with two other anti-CD44 MoAbs, IM7 and S3. Only MoAb S5 significantly increased the engraftment rate of DLA-nonidentical unrelated marrow, whereas the two other anti-CD44 MoAbs were ineffective. The enhanced in vivo effect was not related to differences in the MoAbs' avidities, since both S5 and IM7 had equivalent binding to CD44, but most likely related to the specific epitope that S5 recognizes. Thus, this study shows that the effect of the anti-CD44 MoAb S5 in facilitating engraftment is epitope specific and if one is to use an anti-CD44 to facilitate engraftment of marrow in humans, one cannot assume that any anti-CD44 would work. 相似文献
28.
AF da Silva P McCollum T Szymanska L de Cossart 《Canadian Metallurgical Quarterly》1996,83(10):1370-1372
A total of 700 patients who had carotid endarterectomy (CEA) in the UK and Ireland during a 6-month interval between March and August 1994 were studied prospectively. Some 108 patients (15.4 per cent) had a contralateral internal carotid artery occlusion. Previous reports have shown an associated stroke rate of about 10 per cent in these patients. This study assessed complications and outcome for patients undergoing CEA with contralateral internal carotid artery occlusion compared with those without. The indications for surgery were comparable between the two groups although the patients with occlusion had a slightly higher incidence of arrhythmia and stroke. Intraoperative shunts were used in a significantly higher proportion of those with occlusion (83.3 versus 64.7 per cent, P = 0.0001). The combined death and stroke rate for patients with occlusion was 5.6 per cent compared with 2.4 per cent for the remainder (P not significant). On the basis of the present data, CEA with a contralateral carotid artery occlusion carries only a slight increase in the rate of postoperative stroke and death. This increase was not statistically significant and is lower than that reported previously. 相似文献
29.
B. Herreros G. Lifante A. Kling J.C. Soares M.F. da Silva P.D. Townsend P.J. Chandler J. Olivares J.M. Cabrera 《Optical Materials》1996,6(4):281-286
We present a structural study of two Nd3+/MgO codoped LiNbO3 waveguides fabricated by two different methods: ion-implantation and proton-exchange. Rutherford backscattering spectrometry in combination with channelling was used to study the influence of the waveguide fabrication method on the possible modification of the LiNbO3 crystal structure within the waveguiding layer. The results show that the ion-implanted waveguide mainly maintains the same properties as the virgin crystal, apart from a deterioration of a thin surface layer, whilst the proton-exchanged waveguide exhibits a quite different behaviour, although its surface is less damaged. 相似文献
30.
P Cruz R Almeida M Gon?alves G Marote J Silva C Cavaleiro V Jacinto 《Canadian Metallurgical Quarterly》1994,7(5):277-280
Ocular paresis is a usual diagnosis in neuro-ophthalmologic consultation, and its aetiology is indeed a challenge. The authors studied 3400 records concerning this consultation, between 1982 and the third quarter of 1993. During this period 221 cases with ocular paresis were selected. During this retrospective study we point out the following items: the cranial nerve affected; the neuro-ophthalmologic semiology; the aetiology and clinical evolution, according to the age groups. From 221 cases selected, 111 were paresis from the VIth pair (50.2%), 88 from the IIIrd pair (39.8%), 14 multiple paresis (6.4%) and 8 paresis from the IVth pair (3.6%). The most frequent complaint was diplopia (> 90%). As far as the aetiological diagnosis is concerned, this was easier to establish in patients > 50 years of age. In this age group the most usual aetiology was vascular and traumatic pathologies. In younger patients the most frequent pathologies were traumatic and tumoral. The prognostic was better in the vascular group, the paresis recovery being > 50% in all other pathologies, except the tumoral one. 相似文献